Application of getters to electric incandescent lamps and the like



Patented Ma 3, 1927.

umrao STATES" 1,626,639 PATENT OFFICE.

WILLIAM CHARLES SPROESSER, OF BLOOMFIELD, NEW JERSEY, ASSIGNOR TO WEST- INGHOUSE LAMP COMPANY, A CORPORATION OF PENNSYLVANIA.

APPLICATION OF GETTERS TO ELECTRIC INCANDESCENT LAMPS AND. THE LIKE.

No Drawing.

This invention relates to getters and more particularly to the application thereof to incandescent electric lamps and the like.

An object of my invention is the introduction of getter material into bulbs for evacuated devices in the form of a noncrystalline film on the interior surface thereof.

Another object of my invention is the application of getter material to lamp bulbs and the like by vaporization from an auxil iary filament prior to sealing the regular mount therein. 1

A further object of my invention is the application of' candle-power maintenance material or getter to the inner surface of bulbs for incandescent electric lamps, rather than to the filament thereof, whereby the harmful effect of getter on the filament is obviated.

A still further object of my invention is the manufacture of incandescent electric .lamps and the like with getter material applied initially to the inner surface of the bulb, rather than to the filament.

Other objects and advantages will become apparent as the description proceeds.

The usual method of introducing candle-- power maintenance material or getter intoincandescent electric lamps, is to apply the same from a suspensionon the incandescible filament,- before the same is sealed into the bulb of the lamp. The filament is subsequently incandesced after the lamp has been evacuated, ca'using evaporation or vo'latilization of the getter material and deposition thereof in the .form of a film of finelydivided getter material on the interior of the bulb. Such a film serves as a candle-power maintenance material.

Among the disadvantages of such a method of introducing a getter, is the deleterious effect such material exerts on the filament, to which it has been applied, when the same is incandesced to vaporize it to the bulb. Another disadvantage lies in the fact that a binder is, usually desirable or necessary to hold the etter in place on the filament while handling and after the filament is incandesced the binder is decomposed into gases and vapors which are deleterious tothe operation of the lamp. According to my invention, I obviate the above noted difiiculties and apply the getter material to the inner surface .of the bulb of Application filed August 21, 1923. Serial No. 658,588.

the lamp or the like where it is desired that it shall be placed eventually before the regular mount and filament supported there on is sealed into the bulb.

A prefered method of applying the getter materlal, according tomy invention, con- SIStS 1n employing an auxiliary filament of platinum, nichrome or some other material not readily attacked by the atmosphere when incandesced; applying the desired getter material from a suspension to such a filament, introducing the same temporarily into the lamp bulb and flashing or vaporizing the same from thefilament by means of an electric current passed through the filament. -This operation is preferably performed when the bulb is at least partially exhausted and the getter material is therebydeposited in the form of a: finely-divided film substantially free from moisture and in condition for exerting the desired candlepower maintenance action;

No binder is necessary in applying the getter to the auxiliary filament because it is only necessary that it be held thereon for a very short space of time. For example, an auxiliary filament may be dipped in a suspension of salts of the desired concentration, no binder being mixed therewith, the ettered filament placed within the bulb, the ulb preferably exhaustedand the filament heated to throw off the material to be recondensed on the bulb, after which the auxiliary filament is removed and the regular mount and filament are preferably immediately introduced into the bulb which is then sealed-in and exhausted.

Other means for treating the interior walls of the bulb to obtain getter action were alsotried and may be mentioned as fol- 95 lows: Etching the inner surface of the hull with h drogen fluoride vapor-or a solution thereo washing the interior of the bulb with a concentrated solution of chromic acid; coating the Walls of the bulb with a 100 solution of di-ammonium hydrogen phosphate and applying a solution of getter ma terial to the. bulb. to wet the inner surface thereof and heating the bulb to drive off the moisture therefrom. Although these last 105 methods are mentioned as possibilities, I prefer to apply the getter to the inner sur face of the lamp bulb by vaporization from an auxiliary filament to which it has been applied as described.

My invention will be better understood by the following more detailed description of a preferred method of practicing the same.

I shall consider the application of getter according to my invention as a pregettering operation, because the getter is applied to the inner surface of the bulb, prior to scaling the mount and filament therein, mstead of as heretofore from said filament after said sealing-in and heating the same. In such a pregettering operation, a n1- chrome filament has been used, but it is obvious that platinum or other material which is not attacked by the getter material and which is resistant to oxidation or other attack-when incandesced, may be used.

The auxiliary filament, which should necessarily be strong enough for the 'pur ose and which may be about 20 mils thic 1 s preferably mounted on a stem and dipped-1n a suspension of cryolite or any desired getter material in methyl alcohol or other nonaqueous liquid of similar properties, the use of a binder being unnecessary and preferably not being used. The exact proportion of cryolite and methyl alcohol necessary for the desired results is preferably determined in a series of preliminary tests, the proportion being so regulated that after flashing, the deposit of cryolite is just visible to the naked eye. The use of the mixture 'in the proportion of 30 grams of cryolite to 150 cc. of methyl alcohol has been found to give the best results.

After drying, the gettered auxiliary filament may be inserted into the bulb, which may be supported by an ordinary sealing-in holder. If the flashing operation is conducted at atmospheric pressure, that is, when the bottom of the bulb is not stoppered, it may be found that after flashing, the getter material is not evenly distributed over thewalls of the bulb. It is preferable that the bottom of the bulb. be stoppered and connected with means for creating a partial vacuum therein. If such is done, there will result a great increase in the impact of the 'cryolite particles against the glass surface when the auxiliary filament is connected to a source of electricity and heated to incan-- 1 descence. Accordingly, the auxiliary-filament is preferably incandesced and placed in the bulb in a partial vacuum.

The better the vacuum, the better the condition of the deposited film for candle-power maintenance purposes. One of the most 1mportant effects of conducting the flashing in the vacuum is the elimination of moisture. It'has been found that any substance havingcandle-power maintenance action loses this pro erty when exposed even for a short period, to atmospheric conditions. It is thought that this is because atmospheric moisture'promotes crystallization of the salt, which thereby is placed in a condition where getter action is practically destroyed. The bulb is therefore preferably immediately stoppered til just previous to sealing-in; the sealing-in process following as closely after the flashsealing the regular mount into the bulb, the

bulb may be exhausted and if desired, vaporized phosphorus or other clean-up material may be introduced into the bulb during the exhausting operation, although, as an alternative, such material inay be applied to the filament before sealing-in. After exhausting the lamp may betipped off as is usual.

Upon testing lamps manufactured according to my invention, it is found that an increase in life was effected by the pregettermggoperation.

tching the walls of the bulb with hydrogen fluoride was tried using two different methods. In one, the bulb was closed at one end and filled with a dilute solution of hydrogen fluoride. The solution was allowed to remain in the bulb until etching had proceeded to the desired extent, after which the bulb was thoroughly dried and sealed-in. Using the other method of etching, the bulb was placed over a crucible containing a concentrated solution of hydrogen fluoride. The solution was heated to the desired temperature to evolve hydrogen fluoride to etch the glass. Care was taken to perform this operation under enough suction to catch the poisonous fumes of hydrogen fluoride. and avoid danger to the operator. This h drogen fluoride treatment of the bulb di not give as good results as that obtained by the use of an auxiliary filament.

afterflashing and not opened unany grease or other organic matter is removed. The results secured were not as good as those using an auxiliary filament. Di-ammonium hydrogen phosphate NH ,HPO; was deposited'on the walls of the bulb by dipping in a solution of the salt and then evaporated to dryness. The results secured by this method were not as good as when using an auxiliary filament;

Inpregettering lamps to my invention, any clean-u agent suc as phosphorus which it may desired to introduce,

may be appliedon the arbor of the regular mount of a lamp, thereby makingilit unnecessaryto apply any material to t a re filament, although it is obvious that -i desired, the cleanup material may be applied to the filament, the candle-power maintesubsequently nance ingredient or getter being preferably applied by means of an auxiliary filament as heretofore described.

Although I have described what is now considered a preferred method of practicing my invention, it is to be understood that the same is merely illustrative and that variations in the getter material used and modifications in the method of applying the same,

1 may be employed without departing from the spirit and scope of my invention, as defined by the appended claims.

What is claimed is:

1. The method of gettering incandescent electric lamps and the like comprising vaporizing a candle-power maintenance materia on the inner prior to sealing a regular mount therein and sealing therein an illuminating body having its surface free from said candle power maintenance material.

2. The method of gettering incandescent electric lamps and the like comprising applying a getter material to an auxilia filament, introducing the same into a bulb, heating the filament to vaporize the getter to the interior surface of the bulb and subsel cent lam surface of the bulb thereof,

(fluently introducingrinto the bulb the main i luminating body ee from said getter material.

3. The method of gettering incandescent electric lamps and the like comprising coating an auxiliary filament with a non-aqueous suspension of a getter material, temporarily inserting said filament into the lamp bulb, exhausting said bulb and flashing said filament to vaporize the getter therefrom, removing the auxiliary filament, introducing and sealing-in the regular filament free from Sal?) getter material and exhausting said bul 4. The method of gettering an incandescomprising vaporizing a thin layer of a can le power maintenance material onto the interior surface of the bulb from a source independent of the main illuminating body of the lamp and maintaining said illuminating body free from said candle power maintenance material.

In testimony whereof, I have hereunto subscribed my 1923.

WILLIAM CHARLES SPROESSER.

name this 20th day of August, 

